Impurities present in hydrocarbon streams, and particularly from light ends, such as propylene, pose various problems including contamination and of downstream processes, such as propylene polymerization adversely impacting catalyst utilization efficiency and product quality.
Conventionally, methods have been proposed to remove certain impurities, such as carbon dioxide, from gaseous streams which involve the use of liquids, such as solutions containing ethanolamine, ammonia, soda, carbonates and lyes, are ineffective in reducing the impurities to the extremely low levels required for the latest generation of highly selective catalysts in the downstream processes, such as propylene polymerization.
U.S. Pat. No. 3,141,729 discloses another approach which involves the use of solid adsorbent materials, such as molecular sieves, calcium oxide, finely-divided micro-porous silver oxide dispersed in an admixture with aluminum oxide, and supported cogels of divalent and trivalent metals for such purpose.
U.S. Pat. No. 3,865,924 discloses the use of a synergistic mixture of carbonate and alumina for similar purposes, but requires the addition of water since the adsorption reaction is: EQU K.sub.2 CO.sub.3 +CO.sub.2 +H.sub.2 O.fwdarw.2KHCO.sub.3.
U.S. Pat. No. 4,433,981, SLAUGH et al., is directed to the removal of carbon dioxide from a gaseous stream by contacting the stream with an adsorbent prepared by impregnating a porous alumina with an alkali metal or alkaline earth metal oxide or salt decomposable upon calcination, and subsequently calcining the impregnated alumina at about 350.degree. C. -700.degree. C.
In general, alumina is a known adsorbent in many chemical processes, such as the polymerization of olefins, such as ethylene, for the removal of water and small concentrations of methanol, carbonyl-containing compounds and peroxides. However, the use of alumina has certain disadvantages which adversely affect its use as an adsorbent. Among such disadvantages is that alumina is not always effective as an adsorbent for the removal of, for example, CO.sub.2, from gaseous olefin-containing streams which contain CO.sub.2 at low level concentrations, for example, down to 1 ppm.
Molecular sieves have been used as adsorbents for CO.sub.2, but in some instances have been found to be inefficient when used for the removal of CO.sub.2 from a gaseous stream containing low molecular weight olefins, such as ethylene.
Caustic scrubbers, or bulk caustic scrubbers, have been proposed for use as adsorbents for CO.sub.2 from a gaseous stream, but suffer certain disadvantages, including posing safety problems and adding water to the stream.
U.S. Pat. No. 4,493,715 is directed to a process for the removal of CO.sub.2 from a gaseous stream containing at least one C.sub.2 to C.sub.4 olefin which involves contacting the stream with a regenerable calcined alkali metal compound-treated alumina.
U.S. Pat. No. 4,614,729, STAUFFER CHEMICAL COMPANY, discloses the removal of catalyst poisons, such as CO.sub.2, CO, COS, H.sub.2 O, H.sub.2 S, O.sub.2, and acetylenes from hydrocarbon fluids, such as liquified C.sub.2 -C.sub.30 alkenes. The catalyst used for this purpose is alumina treated with an organometallic compounds from Groups II, III and IV.
British Patent No. GB 1,383,611, FARBEWERKE HOECHST, discloses the removal of impurities at levels below 10 ppm from propylene by treating compressed propylene with mineral adsorbents, such as alumina, which may also contain other oxides, such as Na.sub.2 O.
Belgium Patent No. BE 901,355, LABOFINA, is directed to the removal of low level impurities by passing the propylene over alumina treated with trialkyl aluminum. The purified propylene is disclosed as containing less than 30 ppm COS.
U.S. Pat. No. 4,798,711, NOXSO CORP., describes a process for removing nitrogen oxides and/or sulfur oxides from a gas by using an alkali metal-alumina sorbent.
Katalco 59-3 has been disclosed as a dechlorination catalyst which is specially formulated for the removal of chlorides in advertising publications, i.e., product bulletin KAT-59-3-1. As described Katalco 59-3 is to be used principally for the removal of reactive chlorides from natural gases and other hydrocarbon streams by absorption; for the removal of organic chlorides following hydrogenation over a hydro-treating catalyst; and the dehalogenation of combined chloride/fluoride hydrocarbon streams. Katalco 59-3 is disclosed as having a high chloride capacity, and reduces the chloride content of gas streams to below the normal detection level. It is also disclosed as being compatible with liquid hydrocarbons and operates over a wide range of process conditions. As advertised in advertising literature designated CL-211-1, Katalco 59-3 is described as a solid chemical adsorbent for the removal of chlorides from gas streams. It is also disclosed as being useful to purify any dry process stream where there is a need to prevent corrosion or filing of downstream equipment or deactivation of process catalysts.